Some people really don't like to be left alone with their thoughts. For example, some people taking part in a new study preferred to receive an electric shock rather than spend 15 minutes alone in a room with nothing to do. “The human mind wants to engage with the world, even, it appears, if that involves pain,” Timothy Wilson concludes. He is a psychologist who works at the University of Virginia in Charlottesville.

The brains of mammals evolved or changed slowly over generations to watch for dangers and opportunities.“Only humans evolved the ability to think,” he says.“Still, people can become uncomfortable controlling their own thoughts.” They may not be able to guide those thoughts in a pleasing or comforting direction. And that may help explain the popularity of meditation. It's a process in which people learn to control their thoughts and benefit from quiet contemplation (沉思).

For its new study, Wilson's group recruited (招募) 146 college students. The researchers asked each student to sit alone in a room at their lab without any devices, such as cellphones. This solitude lasted for 6 to 15 minutes.

Most participants said they not only had trouble concentrating but also found the experience unpleasant. The researchers then asked 44 of these people to sit alone at home, too. Again, the students had the same reaction as they had in the lab. They found the experience very uncomfortable.

But here's the shocker — quite literally. The scientists asked 18 men and 24 women to sit quietly and just think about anything. Their quiet, alone time lasted for entire 15 minutes. But in this experiment, the participants could give themselves a painful electric shock if they wished. That shock, though, would not make their participation in the experiment end any earlier. Still, 12 men and 6 women chose to receive a shock, rather than just continue to sit in silence.

Psychologist Jonathan Schooler of the University of California, Santa Barbara, did not work on the new study. He says its findings point out how many people find it unpleasant to reflect on issues by themselves. They'd rather suffer pain than bear quiet time alone.